Method and apparatus for bonding layers of resinous material

ABSTRACT

A method and apparatus for bonding at least two films of resinous material such as polyester films to one another wherein at least a portion of one surface of one polyester film is placed contiguous with at least a portion of one surface of the other polyester films adjacent thereto. At least one layer of resinous material such as a layer of polyester is placed adjacent each of the other surfaces of the polyester films to be bonded and opposite the contiguous portions of the surfaces. The contiguous portions of the polyester films to be bonded are compressed against one another by pressure applied to the two outermost layers of polyester. The temperature of the contiguous portions along their interface is raised at least to a bonding temperature of the polyester by energy transmitted through the layers of polyester on each side of the two polyester films. When the energy, and subsequently the pressure, are removed from the polyester films, a bond is formed between the contiguous surfaces of the polyester films.

This is a continuation of application Ser. No. 210,523 filed Dec. 21,1971, now abandoned.

BACKGROUND OF THE INVENTION

This invention generally relates to a method and apparatus for bondingfilms of resinous material to one another and to the article formedthereby. More particularly, the invention relates to bonding polyesterfilms.

Films of resinous material such as polyester films have been availablefor many years, and they have been put to numerous uses. One particularapplication for such films of resinous materials is in the manufactureof bags or packages, for example, for the food packaging industry wherepackages are continually being designed to lessen the work ofhousewives. In particular, frozen or refrigerated food products whichare generally heated or cooked before being served can be packaged inbags formed from films of resinous materials, for example, polyesterfilms. Such bags or packages with their contents can be placed directlyinto a warm oven or in a pot of boiling water so that the foods can beheated or cooked before serving. Polyester films are particularlydesirable for such applications in that they are transparent, durable,and chemically inert, and they have outstanding barrier properties.

In order to form a bag or package from polyester films, the films mustbe bonded together or sealed in some manner. One method of sealingpolyester films is to coat the films with a readily heat-sealablematerial such as polyethylene in the area of the bond and then heat-sealthe coatings to one another. However, bonds formed in this manner aregenerally incapable of withstanding elevated temperatures, for example,the temperature required to cook a roast in an oven. Another method hasbeen to employ a cement material to bond the polyester films together,but such methods present difficult production problems. One other knownmethod for bonding polyester films is to apply heat directly to thepolyester films to be heat-sealed. However, this latter method will notalways form a bond between the polyester films, particularly when thebond is formed under conditions which would permit the bond to be usedfor commercial applications. Further, when a bond is formed between thepolyester films the areas of the films adjacent the bond generallydeteriorate. Thus, even if the bond has sufficient strengthcharacteristics, the areas of the polyester films around the bond willnot have sufficient strength for many commercial applications.

Accordingly, difficulty has heretofore been experienced in forming asatisfactory seal directly between films of resinous material such aspolyester films, and various methods have been substituted which employan intermediate sealing material. Consequently, there is no known methodavailable for directly bonding polyester films to one another which hasextensive commercial applications. In particular, known methods forbonding polyester films do not form a seal capable of withstandingelevated temperatures and which has sufficient strength for many of themost advantageous applications of the film.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus for bondingcontiguous portions of the surfaces of adjacent films of resinousmaterial, although it is particularly advantageous for bonding polyesterfilms which have heretofore been difficult or impossible to directlybond to one another. According to the present invention, at least onelayer of resinous material is placed adjacent at least one side of theadjacent films of resinous material and contigous therewith opposite theportions of the films of resinous material to be bonded to one another.When the portions to be bonded are compressed against one another, theportions become contiguous along the interface formed therebetween, andenergy is transmitted through the layers of resinous material to raisethe temperature of the contiguous portions along their interface to abonding temperature for the resinous material of the films, thus forminga bond between the contiguous surfaces of the layers of resinousmaterial.

The films of resinous material can be bonded to one another by one ofseveral known bonding means where energy is applied to the portions ofthe films to be bonded while they are being compressed, although knownbonding means must generally be slightly modified to provide the layersof resinous material. Energy can be transmitted through the layers ofresinous material by one of several known means for raising thetemperature of two or more contiguous portions along their interface;for example, a bonding means which applies energy in the form of heatdirectly to the layers of resinous material, such as an impulse-heatsealing means, or a bonding means which heats the interface between thecontiguous portions by cyclically compressing the layers of resinousmaterial, such as an ultrasonic welding means.

One preferred means for transmitting heat to the contiguous portion ofthe films of resinous material through the layers of resinous materialis an impulse heat-sealing means which utilizes a pulse of heat to raisethe temperature. One type of impulse heat-sealing means generallycomprises a first jaw member and a second jaw member. When theheat-sealing means is not actuated, the first jaw member is spaced-apartfrom the second jaw member. Upon actuation of the heat-sealing means,the first and/or second jaw members are urged toward one another toapply pressure to a material disposed therebetween. A heating meansdisposed in one or both of the jaw members applies a pulse of heat tothe material from one or both of the opposite sides thereof.

Thus, according to one preferred method of the present invention, twofilms of resinous material such as two polyester films can be bondedtogether by placing a portion of one surface of one polyester filmcontiguous with a portion of one surface of the other polyester film,thus forming an interface between the contiguous portions to be bonded.The contiguous portions of the polyester films are placed between thespaced-apart jaw members of an impulse heat-sealing means such asdescribed above. Four layers of polyester are placed between the othersurface of each of the polyester films and the jaw member oppositethereto. When the heat-sealing means is subsequently actuated, the jawmembers are urged towards one another and against the layers ofpolyester, thus compressing the contiguous portions of the polyesterfilms along their interface. The heating means in each of the jawmembers applies a pulse of heat to the contiguous portions of thepolyester films to be bonded to one another through the four layers ofpolyester film on each side of the two polyester films. The pulse ofheat from each heating means increases the temperature of the contiguousportions to be bonded to a bonding temperature of the polyester, thusforming a bond between the contiguous portions. In addition, it islikely that at least one of the layers of polyester on each side of thebonded polyester films will also be bonded to the polyester films.

The bond formed between the portions of the two polyester films hasimproved strength, particularly, tensile strength, over bonds formed byknown methods. Furthermore, the strength of the bond is very uniformalong its length, and the areas of the polyester films around the bondedcontiguous portions do not deteriorate to any significant extent so thatthey retain substantially all of their previous strength. The bond canalso withstand elevated temperatures. Thus, a bond formed according tothe present invention permits polyester films to be used in manycommercial applications which were heretofore unavailable to polyesterfilms.

The present invention also provides for several modifications of theabove method for bonding films of resinous material such as polyesterfilms to one another. For example, energy can be applied to thecontiguous portions of the polyester films through layers of polyesterplaced adjacent only one side of the polyester films. Anothermodification of the method described above provides for the bondingtogether of at least two films of resinous material such as twopolyester films without layers of polyester film also being bondedthereto. Thus, at least one layer of a fluorocarbon resin material, forexample, the material manufactured by E. I. DuPont de Nemours & Co.,Inc. under the trademark Teflon, can be placed between the contiguousportions of the polyester films to be bonded and the respective jawmembers of the heat-sealing means. The heat from the jaw members istransmitted through the layers of a fluorocarbon resin material toincrease the temperature of the contiguous portions to cause a bond tobe formed therebetween. Bonding of the polyester films in this manneralso creates a bond between contiguous portions of the polyester films;however, the layers of a fluorocarbon resin material will not be bondedto the polyester films.

The layers of resinous material adjacent one or both sides of the filmsof resinous material to be bonded can be formed from a single layer ofresinous material having a described thickness or they can be formedfrom a plurality of layers of resinous material having a combinedthickness equal to a desired thickness. It is believed, however, that aplurality of layers of resinous material provides a better bond betweenthe contiguous portions of the films of resinous material, particularlywhen polyester films are to be bonded, than does the single layer havinga thickness equal to the combined thickness of the plurality of layers.

Accordingly, it is an object of the present invention to provide amethod and apparatus for bonding at least two films of resinous materialsuch as a polyester films to one another, and the article formedthereby.

Another object of the invention is to provide a method and apparatus forforming a bond between at least two films of resinous material such as apolyester film wherein the energy for creating the bond is transmittedthrough at least one layer of resinous material such as a polyester filmadjacent the layers of resinous material to be bonded.

Still another object of the invention is to provide such a method andapparatus wherein the energy is transmitted through four layers ofresinous material such as polyester films adjacent the films of resinousmaterial to be bonded.

Still another object of the present invention is to provide a method andapparatus for forming a bond between at least two films of resinousmaterial such as polyester films wherein the energy for creating thebond is transmitted through at least one layer of a fluorocarbonadjacent the polyester films to be bonded.

These and other objects and advantages of the present invention areapparent from the following description, when read in view of theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of one of the methods of the presentinvention.

FIG. 2 shows one apparatus of the present invention for forming a bondbetween at least two films of resinous material by transmitting energythrough layers of resinous material on both sides of the films to bebonded.

FIG. 3 is a perspective view of a portion of the apparatus of FIG. 2showing two films of resinous material to be bonded and the four layersof resinous material on each side thereof.

FIG. 4 is a cross-sectional view of the jaw members of the apparatus ofFIG. 2 showing the two films of resinous material to be bonded and thelayers of resinous material therebetween.

FIG. 5 shows the two bonds formed across the two films of resinousmaterial by the apparatus of FIG. 2.

FIG. 6 shows two bags or packages formed by the apparatus of FIG. 2.

FIG. 7 shows the apparatus of FIG. 2 having another means for providingthe layers of resinous material on each side of the two films ofresinous material to be bonded.

FIG. 8 shows a bond being formed between two films of resinous materialby heat being transmitted through four layers of resinous materialdisposed on only one side of the films to be bonded.

FIG. 9 shows an upper jaw member of a heat-sealing means having a meansfor providing layers of a fluorocarbon resin material between theheating face thereof and the films of resinous material to be bonded.

FIG. 10 shows one means of assembling two films of resinous material tobe bonded and one layer of resinous material on each of the oppositesides of the two films.

FIG. 11 shows one seal that can be formed from the films of resinousmaterial shown in FIG. 10.

FIG. 12 shows one means of assembling two films of resinous material tobe bonded to one another and two layers of resinous material on each ofthe opposite sides of the two films.

FIG. 13 shows one seal that can be formed from the films of resinousmaterial shown in FIG. 12.

FIG. 14 shows one means of assembling two films of resinous material tobe bonded to one another and four layers of resinous material on each ofthe opposite sides of the two films.

FIG. 15 shows the films of resinous material shown in FIG. 14 after thefilms have been compressed together by pressure applied to the layers ofresinous material.

FIG. 16 shows one seal that can be formed from the films of resinousmaterial shown in FIGS. 14 and 15.

FIG. 17 shows another means of assembling two films of resinous materialto be bonded to one another and four layers of resinous material on eachof the opposite sides of the two films.

FIG. 18 shows still another means of assembling two films of resinousmaterial to be bonded to one another and four layers of resinousmaterial on each of the opposite sides of the two films.

FIGS. 19-22 show one means for forming four additional layers ofresinous material one each side of two films of resinous material.

FIG. 23 illustrates another apparatus for heating and compressing thefilms of resinous material to cause a bond to be formed therebetween.

DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

FIG. 1 diagrammatically illustrates one of the methods of the presentinvention for bonding together at least two films of resinous materialsuch as polyester films. Polyester films are commercially available inthe form of sheets and also tubes, both of which can be used to makepolyester bags or packages for food products. In FIG. 1 a tube ofpolyester film 15 is folded to form two opposing polyester films 10 and11 which can subsequently be bonded to one another at predeterminedintervals along the length of the tube, thus forming individual bags orcompartments therebetween. Thus, the two polyester films 10 and 11 areintermittently advanced along a predetermined path in the direction ofthe arrow passed the various operating points designated A, B, C and D.At station A, the two polyester films 10 and 11 are formed with aportion of one surface of one of the film contiguous with a portion ofone surface of the other film, thus forming an interface between thecontiguous portions. The contiguous portions of the two polyester films10 and 11 to be bonded are subsequently advanced along the path tostation B.

At station B at least one layer of polyester 14 or 15 is placed adjacenteach of the other surfaces of the polyester films 10 and 11 and oppositethe contiguous portions thereof. As will be described more fullyhereinafter, the layers of polyester 14 and 15 can be formed in variousways. For example, each layer of polyester can be separate and distinctfrom the other layers of polyester or the layers of polyester 14 and 15can be formed from a single layer of polyester which is folded uponitself several times to form the required number of layers of polyester.In addition, the layers of polyester 14 and 15 can be formed from acontinuous portion of the polyester films 10 and 11. The continuousportions can be folded in one of various ways about the contiguousportions of the polyester films 10 and 11 to be bonded, therebyproviding the layers of polyester 14 and 15 on both sides thereof.

Once the layers of polyester 14 and 15 are formed adjacent to thecontiguous portions of polyester films 10 and 11, the polyester films 10and 11 are advanced to station C where the continguous portions of thesurfaces of the polyester films 10 and 11 are bonded to one another. Asdescribed above, the bonding can be accomplished by any one of severalknown bonding means. The bonding means 17 schematically illustrated inFIG. 1 is an impulse heat-sealing means having a first jaw member 18 anda second jaw member 19. When the impulse heat-sealing means 17 is notactuated, the first jaw member 18 is spaced-apart from the second jawmember 19. Upon actuation of the heat-sealing means 17, the first andsecond jaw members 18 and 19 are urged towards one another to applypressure to the layers of polyester on each side of the polyester films10 and 11, thus compressing the contiguous portions of the polyesterfilms 10 and 11 to be bonded to one another. A heating means in each ofthe jaw members 18 and 19 applies a pulse of heat to the contiguousportions of the polyester films 10 and 11 through each of the layers ofpolyester 14 and 15. The pulses of heat from the jaw members 18 and 19increase the temperature of the contiguous portions of the polyesterfilms 10 and 11 along their interface to at least a bonding temperaturefor the polyester. Once the pulse of heat has been applied, the pressureis preferably maintained by the jaw members 18 and 19 until the bond issecurely formed between the contiguous portions of the polyester films.

The contiguous portions of the polyester films 10 and 11 which are nowbonded to one another, and the layers of polyester 14 and 15 which arealso bonded thereto can be subsequently advanced to a trimming station Dwhere the compartments formed in the tube of polyester are separatedfrom one another, thus forming polyester bags having an opening at oneend. The trimming means 22, which can be one of several such means knownin the art is schematically illustrated in FIG. 1 as a knife or blade 23cooperating with a fixed backing member 24 to cause a shearing actiontherebetween.

Now referring to FIGS. 2-4, an impulse heat sealing means 25 for forminga plurality of bags or packages from a continuous web or sheet ofresinous material such as polyester is shown. The heat-sealing means 25is adapted to receive the web of polyester 26 after it has been foldedin accordance with a known side weld bag forming technique wherein bothouter portions 11 of the web 26 are folded upon the central portion 10of the web so that the edges of the web are adjacent one another alongthe longitudinal axis 27 of the web. Thus, the central portion of theweb forms one polyester film 10, and the outer portions of the web formtwo polyester films 11 to be bonded to the polyester film 10. As will bedescribed below, the impulse heat-sealing means 25 forms a pair ofspaced apart bonds across the width of the web at preselected intervalsalong the length of the web. Thus two bags or packages are formedbetween the last bond of one pair of bonds and the first bond of thenext pair of bonds.

Accordingly, referring to FIGS. 2, the impulse heat sealing means 25comprises the two opposing jaw members 18 and 19. The jaw members aremounted to the frame 28 of the sealing means 25 for movement between thefirst position and a second position. In the first position, the jawmembers 18 and 19 are spaced-apart as illustrated in the figure. Whenthe sealing means is actuated, the jaw members 18 and 19 move to thesecond position wherein the members are urged towards one another tocompress a material disposed therebetween. The web of polyester film 26is shown advancing between the spaced-apart jaw members 28 and 29.Referring now to FIG. 3, the folded web of polyester 26 is advancedalong a predetermined path indicated by the arrow between thespaced-apart jaw members 17 and 18 by means of several pairs of rubberwheels 29 disposed on both sides of the jaw members along each of thefolded edges of the folded web 26. One of the wheels of each pair ofrubber wheels 29 is mounted on each side of the web 26 and the twowheels are urged against one another. The pairs or rubber wheels 28 areintermittently and simultaneously rotated in synchronism with themovement of the jaw members between the first and second positions tointermittently advance the folded web of polyester film 26 between thespaced-apart jaw members 18 and 19 of the impulse heat sealing means 25.

The layers of polyester 14 and 15 which transmits the energy for heatingthe polyester films to be bonded are shown in FIGS. 2-4. The layers ofpolyester 14 and 15 are strips of polyester having four separate layersof polyester in each strip. Two supply spools 30 and 31 are pivotallymounted on one side of the frame 28 for supplying the strips ofpolyester 14 and 15 in the direction of the arrows and two take-upspools 32 and 33 are mounted on the other side of the frame 29 forretrieving the unutilized portion of the strips, as will be describedhereinafter. The strips of polyester 14 and 15 extend across the top andbottom of the folded web of polyester 26 and between the web and therespective jaw members 18 and 19 of the sealing means 25. Thus, when theimpulse heat sealing means is actuated, the jaw members 18 and 19 areurged towards one another and press the strips of polyester 14 and 15against the folded web of polyester film 26. The pressure from the jawmembers compresses a portion of one surface of each polyester film 11against a portion of one surface of the polyester film 10, therebyforming an interface between the contiguous portions.

Now referring to FIG. 4, a cross-sectional view of the jaw members 18and 19 compressing the contiguous portions of the polyester films 10 and11 is shown. As noted above, the strips of polyester 14 and 15 have fourseparate layers of polyester therein. Each jaw member 18 or 19 has twomeans 40 disposed adjacent the heating face 41 thereof for generating apulse of heat when the impulse heat sealing means is actuated and thejaw members 18 and 19 have moved to the second position illustrated inFIG. 4. The two heat pulse generating means 40 in each jaw member 18 or19 are spaced apart, extend substantially the length of the jaw member,and are disposed opposite the corresponding heat pulse generating means40 in the other jaw member. Thus, the pulses of heat form each pair ofopposing heat pulse generating means 40 are transmitted through one ofthe strips of polyester 14 or 15 and increase the temperature of thecontiguous portions of the polyester films 10 and 11 along the separateportions 42 of the interface between the pair of opposing generatingmeans 40. The temperature of the contiguous portions at the portions 42of the interface is increased to a bonding temperature for thepolyester, thus causing two separate, spaced-apart bonds to be formedbetween the contiguous portions of the polyester films 10 and 11 acrossthe width of the folded web of polyester film 26. As the pulses of heatsubsides, the pressure exerted by the jaw members 18 and 19 ispreferably maintained to permit the two separate bonds to be securelyformed between the polyester films 10 and 11.

Still referring to FIG. 4, one means for severing or trimming the bondsformed between the polyester films 10 and 11 thus forming separate bagsfrom the folded web of polyester 26 is illustrated. The severing means50 is mounted in the upper jaw member 19 of the impulse heat sealingmeans 25. The severing means 50 includes a cutter 51 having two separateblades 52 and 53. The two blades 52 and 53 of the cutter 51 extendacross the width of the folded web of polyester 26 and slightly beyondeach longitudinal folds formed therein. Each end of the blade 52 iscurved in the direction of advance of the web, while each end of theblade 53 curves in the opposite direction. The purpose of having a pairof blades of this shape will be shown below. The cutter 51 is mountedwithin the upper jaw member 19 for movement between a first position anda second position in response to the position of the jaw members. Whenthe jaw members 18 and 19 are spaced-apart, the cutter 51 is in thefirst position where it is withdrawn into the recess 54 in the upper jawmember 19, as illustrated by the dashed lines in FIG. 4. When the jawmembers 18 and 19 are urged towards one another, the cutter 51 moves tothe second position, as shown in the figure, where the blades 52 and 53are extended for engagement with the respective grooves 55 and 56 in theheating surface 41 of the lower jaw member 18. Thus, the blades 52 and53 sever the strips of polyester 14 and 15 and the folded web ofpolyester 26 along two spaced-apart planes between the two bonds formedat the interface of the contiguous portions of the polyester films 10and 11.

As noted above, the bonds 60 and 61 are formed between the polyesterfilms 10 and 11 across the width of the folded web of polyester 26. Thetwo spaced-apart bonds 60 and 61 formed between the polyester films 10and 11 of the folded web of polyester 26 are shown in FIG. 4. The dashedlines 62 and 63 therein are the lines along which the blades 52 and 53of the cutter 51 sever the strips of polyester 14 and 15 and the foldedweb 26. Thus, once the strips of polyester 14 and 15 have been severed,thin ribbons of polyester 65 and 66 remain attached to the respectivestrips of polyester 14 and 15 at the one side of the impulseheat-sealing means 25. These ribbons of polyester 65 and 66 are wound upon the take-up spools 32 and 33, respectively, and serve to pull thestrips of polyester 14 and 15 into position in preparation for formingthe next pair of spaced-apart bonds in the folded web 26. Thus, a meansfor rotating the take-up spools 32 and 33 in the direction of the arrows(not shown) is synchronized with the jaw members 18 and 19 and the pairsof rubber wheels 29 so that the new strips of polyester 14 and 15 arebeing pulled or advanced adjacent both sides of the folded web ofpolyester 26 as the web is being advanced by the rubber wheels 29between the spaced-apart jaw members 18 and 19 of the impulseheat-sealing means 25.

Once the folded web of polyester 26 has been advanced a predetermineddistance, for example, the width of the bags or packages to be formedfrom the folded web 26 and new strips of polyester 14 and 15 are inposition, the jaw members 18 and 19 of the heat-sealing means 25 can beactuated to form two more spaced-apart bonds 60 and 61 between thepolyester films 10 and 11 across the width of the folded web 26. Twopolyester bags 70 and 71 are thus formed in the folded web of polyester26 between the bond 61 previously formed between the polyester films 10and 11 and the new bond 60. Referring to FIG. 6, the two bags 70 and 71are shown after the central portion of the folded web of polyester 27between the two bonds 60 and 61 has been severed along the longitudinalaxis 27 thereof.

Other means are available for sequentially advancing or pulling thestrips of polyester 14 and 15 across the folded web of polyester 26 andinto position for a bond to be formed therein. For example, FIG. 7 showsone modification of the impulse heat sealing means 25 of FIG. 2 whichwill also advance the strips of polyester 14 and 15 adjacent to eachside of the folded web 26. The spaced-apart jaw members 18 and 19 andthe two supply spools 30 and 31 for the strips of polyester 14 and 15are provided as described in FIG. 2. The strips of polyester 14 and 15pass between the pairs of guide rollers 75 and 76 and through two slots77 and 78 on the one side of the impulse heat sealing means 25, thuspositioning the strips of polyester 14 and 15 on the one side of thespaced apart jaw members 18 and 19. In addition, two pistons 79 and 80are mounted on the other side of the impulse heat sealing means 25 sothat the piston rods 81 and 82 of the respective pistons extend inplanes parallel to the plane of the folded web of polyester and alongpaths perpendicular to the path of travel of the folded web of polyester26. The piston rods have L-shaped members 83 and 84 mounted thereto forpositioning the free ends of the strips of polyester 14 and 15 on theother side of the spaced apart jaw members 18 and 19. When the strips ofpolyester 14 and 15 are positioned as shown in FIG. 7, the impulse heatsealing means 25 can be actuated to form at least one bond across thewidth of the folded web of polyester 26 in the manner described above.In addition, the jaw members 18 and 19 include two cutting means 85 and86 for cutting the strips of polyester 14 and 15 on both sides of thefolded web 26 along lines parallel to the path of travel of the web.Once the strips of polyester are cut and the bond is formed in the web,the jaw members 18 and 19 can return to their spaced apart position andthe folded web of polyester 26 can be advanced in preparation for theforming of another bond therein.

While the web of polyester 26 is advancing, the pistons are actuated andthe piston rods 81 and 82 extend along paths on opposite sides of thefolded web of polyester 26 with the portions 87 and 88 of the L-shapedmembers 83 and 84 passing between the folded web and one of the jawmember 18 or 19. When the piston rods 81 and 82 are fully extended, theL-shaped members 83 and 84 are adjacent the slots 77 and 78 in the frame28 on the opposite side of the impulse heat sealing means 25, and thefree ends of the strips of polyester 14 and 15 which are extendingtherethrough. A gripper 89 on the portion 87 of the L-shaped member 83on the upper piston rod 81 grips the free end of the strip of polyester15 which is held by the upper slot 77 and similar lower gripper 90 onthe lower piston rod 82 grips the free end of the strip of polyester 14.Thus, as the piston rods 81 and 82 are subsequently being retracted tothe positions shown in FIG. 7, the grippers 89 and 90 pull the free endsof the strips of polyester 14 and 15 with them thereby placing one stripof polyester 14 or 15 between each of the spaced-apart jaw members 18and 19 and the portion of the folded web of polyester 26 therebetween.Once the pistons are fully retracted and the web of polyester has beenadvanced, another bond can be formed therein.

As noted above, a bond can also be formed between the contiguousportions of films of resinous material by energy transmitted through atleast one layer of resinous material on only one side of the polyesterfilms. For example, one means for bonding two polyester films 10 and 11by applying heat to the contiguous portions of the films through fourlayers of polyester 14 on only one side of the polyester films is shownin FIG. 8. The jaw members 18 and 19 apply pressure to compress thecontiguous portions of the polyester films 10 and 11 along theirinterface. Unlike the jaw members 18 and 19 of FIG. 4, heat is onlyapplied by one heating means 40 disposed in jaw member 18 to raise thetemperature of the contiguous portions along their interface to abonding temperature for the polyester, thus forming a bond between thepolyester films 10 and 11.

Although the bond formed between the polyester films described abovehave been formed by providing layers of polyester through which theenergy is transmitted, layers of a fluorocarbon resin material such asTeflon can also be used for the bonding of polyester films. However,unlike the layers of polyester, the layers of a fluorocarbon resinmaterial will not be bonded to the polyester films. Therefore, the samelayers of a fluorocarbon resin material can be used to form severalbonds in the polyester films. Thus, referring to FIG. 9, a modified formof an upper jaw member 18 is shown which has a sheet of a fluorocarbonresin material 90 attached thereto. The sheet 95 extends substantiallythe length of the jaw member 18 and is preferably a plurality ofseparate layers, for example, four layers of a fluorocarbon resinmaterial. A supply roll 96 of the fluorocarbon resin material sheet 15is mounted on the top of the jaw member 18 and the sheet of afluorocarbon resin material extends from the supply roll 96 around theheating face 41 of the jaw member 18 to the recovery roll 97. A means(not shown) for incrementally unwinding the sheet 95 from the supplyroll 96 to the recovery roll 97 is preferably provided to advance thesheet of a fluorocarbon resin material 95 across the heating face 41 ofthe jaw member 18 in response to actuation of the impulse heat sealingmeans 25. Thus, a layer of a fluorocarbon resin material 95 is alwaysdisposed between the heating means 40 of the jaw member and thepolyester films 10 and 11 to be bonded to one another. The incrementaladvance is such that a portion of the sheet of a fluorocarbon resinmaterial 95 is used for forming only several bonds, for example, 5 or 6bonds, before it is wound past the face 41 and onto the recovery roll97.

EXAMPLE 1

By way of example, two polyester films each approximately 0.0005 inchesthick were placed with a portion of one surface of one of the filmscontiguous with a portion of one surface of the other film. Thecontiguous portions of the polyester films were placed between the jawmembers of an impulse heat-sealing means. One layer of Teflonapproximately 0.002 inches thick was placed between each of the jawmembers of an impulse heat sealing means and the other surface of eachpolyester film. The jaw members compressed the layers of polyester andthe polyester films with a sealing pressure of about 10-12 pounds perlinear inch of seal, and a pulse of heat was applied to the contiguousportions of the polyester films through the layer of Teflon on each sideof the film. The heat pulse had a duration of about 31/2 seconds, andthe jaw members continued to compress the polyester films for about 5seconds after the heat pulses were discontinued. When the pressure wasalso removed, a bond was formed between the contiguous portions of thepolyester films; however, a bond was not formed between the twopolyester films and the layer of Teflon on either side thereof.

FIGS. 10, 12, 14, 17 and 18 illustrate several ways that the layers ofpolyester 14 and 15 can be formed adjacent the polyester films 10 and 11to be bonded. Thus, referring to FIG. 10, one layer of polyester 14 or15 is formed adjacent the other surface 100 or 101 of each of the twopolyester films 10 and 11 with a portion thereof opposite the portions102 and 103 of the one surfaces 104 and 105 to be bonded to one another.The layers of polyester 14 and 15 are a continuation of the polyesterfilms 10 and 11 which are folded in opposite directions above theportions 102 and 103 thereof to be bonded so as to overlie the portions.By way of example, in the heat sealing means 25 of FIG. 2, the jawmembers 18 and 19 could apply pressure and heat to the layers ofpolyester 14 and 15 at the points indicated by the arrows in FIG. 10 andthe bond formed thereby could subsequently be severed along the dashedline, thus forming the seal between the polyester films 10 and 11illustrated in FIG. 11.

FIG. 12 illustrates another way of forming the layers of polyester 14and 15 adjacent and opposite the portions 102 and 103 of the polyesterfilms 10 and 11 to be bonded to one another. In the figure, two layersof polyester 106 and 107 or 108 and 109 are provided on each of theopposite sides of the two polyester films 10 and 11. The layers ofpolyester 106 and 109 and the two layers 107 and 108 are formed from twocontinuous layers of polyester wrapped around the free ends of the twopolyester films 10 and 11. As described above, the pressure and heat canbe applied to the additional layers of polyester 14 and 15 at the pointsindicated by the arrows. The seal formed when the bond formed therebyhas been subsequently severed along the dashed lines is illustrated inFIG. 13.

FIGS. 14, 17 and 18 illustrate several ways that four layers ofpolyester 14 and 15 can be formed on each of the opposite sides of thepolyester films 10 and 11. Referring first to FIG. 14, the four layersof polyester 14 or 15 on each side of the polyester films 10 and 11 areformed from a single layer of polyester 110 or 111 folded in the shapeof a "W" so as to provide four additional layers of polyester adjacentand opposite each of the portions 102 and 103 of the polyester films 10and 11 to be bonded to one another. FIG. 15 shows the four layers ofpolyester 14 and 15 of FIG. 7 after the layers have been compressed bythe jaw members 18 and 19 the bonding means of FIG. 1, thus placing theportions 102 and 103 of the polyester films 10 and 11 contiguous withone another. FIG. 16 illustrates the seal that can be formed from thepolyester films 10 and 11 illustrated in FIG. 14 and 15 after thecontiguous portions of the polyester films 10 and 11 have been bonded toone another and the bond has been severed along the dashed lines inFIGS. 14 or 15.

FIG. 17 illustrates another way of forming four layers of polyester 14and 15 on each of the opposite sides of the polyester films 10 and 11.As shown therein, the layers of polyester 14 and 15 are formed fromcontinuous portions 115 and 116 of the polyester films 10 and 11. Whenthe portions 115 and 116 are folded as showon in FIG. 17, they providefour layers of polyester 14 and 15 on each of the opposite sides of thetwo polyester films 10 and 11.

EXAMPLE 2

By way of example, two polyester films each approximately 0.0008 inchesthick were placed with a portion of one surface of the films contiguouswith a portion of one surface of the other film. The contiguous portionsof the polyester films were placed between the jaw members of an impulseheat-sealing means and four layers of polyester each approximately0.0008 inches thick were placed between each of the jaw members and theother surface of each polyester film. The layers of polyester wereformed adjacent the polyester films as shown in FIG. 17. The jaw memberscompressed the layers of polyester and the polyester films with asealing pressure of about 10-12 pounds per linear inch of seal, and apulse of heat was applied to the contiguous portions of the polyesterfilms through the four layers of polyester on each side of the films.The heat pulse had a duration of about 21/2 seconds, and the jaw memberscontinued to compress the polyester films for about 5 seconds after theheat pulse ended. When the pressure was also removed, a bond was formedbetween the contiguous portions of the polyester films, and a bond wasalso formed between the two polyester films and the four layers ofpolyester on each side thereof.

EXAMPLE 3

By way of further example, two polyester films each approximately 0.0005inches thick and eight layers of polyester each approximately 0.0005inches thick were placed between the jaw members of an impulseheat-sealing means as described in Example 2. The jaw members compressedthe layers of polyester and the polyester films with a sealing pressureof about 10-12 pounds per linear inch of seal, and a pulse of heat wasapplied to the contiguous portions of the polyester films through thefour layers of polyester on each side of the films. The heat pulse had aduration of about 21/2 seconds, and the jaw members continued tocompress the polyester films for about 5 seconds after the heat pulseended. When the pressure was also removed, a bond was formed between thecontiguous portions of the polyester films, and a bond was also formedbetween the two polyester films and the four layers of polyester on eachside thereof.

FIGS. 19-21 illustrate one means for folding the continuous portions 115and 116 of the polyester films 10 and 11 to form the four layers ofpolyester 14 and 15 shown in FIG. 17. Referring to FIG. 19, the twopolyester films 10 and 11, advancing along a predetermined pathindicated by the arrow, are folded by fingers or guides 120 and 121 sothat the continuous portions 115 and 116 of the polyester films overliethe contiguous portions 102 and 103 of the polyester films 10 and 11 tobe bonded, thus forming two layers of polyester of one side of thepolyester films 10 and 11. Next, guides 122 and 123 fold the continuousportions 115 and 116 back on themselves so that four layers of polyester14 are formed on one side of the polyester films 10 and 11 as shown inFIG. 20. Referring now to FIG. 21, the continuous portions 115 and 116are subsequentially folded by guides 124 and 125 so that the continuousportions 115 and 116 also overlie the contiguous portions 102 and 103 onthe other side of the polyester films 10 and 11, thus forming two layersof polyester on that side of the films. Finally, as shown in FIG. 22,guides 126 and 127 fold the continuous portions 115 and 116 of thepolyester films 10 and 11 back on themselves so that four layers ofpolyester 14 and 15 are alternately formed on each side of the polyesterfilms 10 and 11. The guide rollers 128 and 129 can then advance thepolyester films 10 and 11 and the layers of polyester 14 and 15 formedto a bonding means where a bond can be formed between the contiguousportions 102 and 103 of the films.

Finally, FIG. 18 illustrates still another way of providing four layersof polyester 14 and 15 adjacent the polyester films 10 and 11 andopposite the portions 102 and 103 thereof to be bonded to one another.As illustrated therein, each of the four layers of polyester 14 and 15are separate and distinct from the other layers of polyester.

As noted above, a bond can be formed between films of resinous materialby transmitting ultrasonic vibrational energy through layers of resinousmaterial on each side of the layers to be bonded. By way of example, onetype of ultrasonic vibrating means is disclosed in U.S. Pat. No.3,224,915, issued Dec. 21, 1965. Referring to FIG. 23, an ultrasonicvibrating means 140 is illustrated forming a bond between two films of aresinous material such as polyester films 10 and 11. The vibrating means140 comprising a stationary anvil 141 and an ultrasonic vibrating member142. The member 142 vibrates in the directions indicated by the arrows.Four layers of polyester 14 and 15 are placed between the polyesterfilms 10 and 11 to be bonded and the anvil 141 and vibrational member142, respectively. When the vibrating means is actuated, the ultrasonicvibrations of the member 142 compress the contiguous portions 102 and103 of the polyester films 10 and 11 along their interface and generateheat which increases the temperature of the contiguous portions of thepolyester films 10 and 11 along their interface to a temperature atleast as high as the bonding temperature of the resinous material, thusforming a bond between the polyester films.

EXAMPLE 4

By way of example, two polyester films each approximately 0.00092 inchesthick and eight layers of polyester each approximately 0.00092 inchesthick were formed as described in Example 2. The polyester films and thelayers of polyester were placed between the anvil and the vibrator of anultrasonic welding machine of the type generally illustrated in FIG. 23.The anvil was a one-eighth inch wide wheel having a diameter of 3 3/16inches. The vibrator had a crowned working surface having a 10 inchradius and it vibrated with an amplitude of approximately 0.001 inches.The vibrator and anvil were urged towards one another with a 90 poundforce. Whe the polyester films and the layers of polyester were advancedbetween the vibrator and the anvil at about 1 inch per second, a bondwas formed between the contiguous portions of the polyester films, and abond was also formed between the films and the layers of polyester oneach side thereof.

Other modifications and variations of the invention will be apparent tothose skilled in the art, and they may be made without departing fromthe spirit and scope of the present invention which is claimed herein.

I claim:
 1. A seal formed between at least two films of resinousmaterial having a portion of at least one surface of each film ofresinous material being contiguous with a portion of a surface ofanother film of resinous material, the seal comprising a bond formedbetween each of the contiguous portions of the surfaces of the films ofresinous material, the bond being formed by heating and compressing thecontiguous portions of the films of resinous material, the contiguousportions of the films of resinous material being compressed by pressureapplied to additional outermost layers of resinous material disposedadjacent the other surfaces of each of the contiguous films of resinousmaterial and opposite to the contiguous portions thereof, the contiguousportions of the surfaces of the films of resinous material whilecompressed being heated to a temperature at least as high as the bondingtemperature of the resinous material of the films through the layers ofresinous material adjacent thereto by energy applied to each of theother surfaces of the outer films of resinous material, said outermostlayers being adhered to the other surfaces of the contiguous films.
 2. Amethod for bonding portions of first and second films of polyesterresinous material to one another, the polyester resinous material beingof a type which is not bondable by application of conductivelytransferred heat and pressure directly to only the two films by reasonof deterioration of the two films about the periphery of the seal zonewhen the heat and pressure are applied, the method comprising the stepsof:a. providing at least first and second films of polyester resinousmaterial to be bonded to one another and at least one direct-heatisolating film of polyester resinous material; b. disposing a portion ofone surface of the first film of polyester resinous material contiguouswith a portion of one surface of the second film of polyester materialfor forming an interface between the contiguous portions; c. placing onesurface of the direct-heat isolating film of polyester resinous materialadjacent the other surface of the portion of at least one of the firstand second films of polyester resinous material disposed contiguous withthe portion of the other film of polyester resinous material, the onesurface of the direct-heat isolating film of polyester resinous materialbeing exposed; d. compressing the contiguous portions of the first andsecond films of polyester resinous material against one another alongthe interface thereof by pressure applied to the exposed other surfaceof the direct-heat isolating film of polyester resinous material; e.applying energy for conductively heating the contiguous portions of thefirst and second films of polyester resinous material along theirinterface to raise the temperature thereof to at least the bondingtemperature of the polyester resinous material of the first and secondfilms of polyester resinous material and to cause a bond to be formedbetween the contiguous portions of the first and second films ofpolyester resinous material, the energy being applied by a member havinga face portion which is moved directly into contact with the othersurface of the direct-heat isolating film of polyester resinous materialfor conductively transmitting energy for heating by conduction throughthe exposed other surface of the direct-heat isolating film of polyesterresinous material, the applied energy being sufficient to fuse thedirect-heat isolating film of polyester resinous material against theother surface of the one of the first and second films of polyesterresinous material to enhance the transfer of energy for heating thecontiguous portions of the first and second films to the bondingtemperature while causing the direct-heat isolating film to be bonded tothe other surface, the direct-heat isolating layer preventing the regionof the first and second films adjacent the bond formed therein frombeing raised to a temperature which would cause degradation thereof; andf. discharging the bonded first and second films of polyester resinousmaterial and the bonded direct-heat isolating film of polyester resinousmaterial through which the energy has been applied from the location atwhich the bond is formed.
 3. A method in accordance with claim 2 inwhich the contiguous portions of the first and second films of resinousmaterial remain compressed against one another when the energy appliedthrough the direct-heat isolating film of polyester resinous materialfor heating the contiguous portions of the first and second films ofresinous material is terminated.
 4. A method in accordance with claim 2in which the step of placing a direct-heat isolating film of polyesterresinous material adjacent the other surface of the portion of at leastone of the first and second films of polyester material comprisesplacing at least two direct-heat isolating films of polyester resinousmaterial, each of the direct-heat isolating films of polyester resinousmaterial being placed adjacent the other surface of a different one ofthe first and second films of resinous material opposite the contiguousportions of the first and second films of resinous material, the energyfor heating the contiguous portions of the direct-heat isolating filmsof polyester resinous material along their interface being appliedthrough each of the direct-heat isolating films of polyester resinousmaterial.
 5. A method in accordance with claim 4 and further comprisingan even number of direct-heat isolating films of polyester resinousmaterial, one-half of the even number of direct-heat isolating films ofpolyester resinous material being placed on each of the opposite sidesof the first and second films of resinous material and adjacent theother surface of the film of resinous material on the respective side aportion of one surface of one of the direct-heat isolating films ofpolyester resinous material on each side of the first and second filmsof resinous material being contiguous with the other surface of a filmor resinous material opposite the contiguous portions of the first andsecond films of resinous material each of the other direct-heatisolating films of polyester resinous material on each side of the firstand second films of resinous material being contiguous with a portion ofa surface of another of the direct-heat isolating films of polyesterresinous material, the direct-heat isolating films of polyester resinousmaterial being contiguous with one another opposite the contiguousportions of the first and second films of resinous material, the energyfor heating the contiguous portions of the direct-heat isolating filmsof polyester resinous material along their interface being appliedthrough the direct-heat isolating films of polyester resinous materialon each of the opposite sides of the first and second films of resinousmaterial.
 6. A method in accordance with claim 5 and further definedwherein eight direct-heat isolating films of polyester resinous materialare provided, four of the direct-heat isolating films of polyesterresinous material being placed on each of the opposite sides of thefirst and second films of resinous material.
 7. A method in accordancewith claim 4 and further defined wherein each of the first and secondfilms of resinous material have approximately the same thickness.
 8. Amethod in accordance with claim 7 in which each of the direct-heatisolating films of polyester resinous material have approximtely thesame thickness as the thickness of each of the first and second films ofresinous material.
 9. A method in accordance with claim 4 in which atleast one of the direct-heat isolating films of resinous materialadjacent to the other surface of at least one of the first and secondfilms of resinous material is folded over from a continuous portion ofone of the first and second films of resinous material.
 10. A method inaccordance with claim 4 in which at least two of the direct-heatisolating films of polyester resinous material on at least one side ofthe first and second films of resinous material are folded over from asingle continuous sheet of resinous material.
 11. A method in accordancewith claim 4 in which the contiguous portions of the first and secondfilms of resinous material are compressed against one another alongtheir interface by pressure applied to the direct-heat isolating filmsof polyester resinous material on both sides of the first and secondfilms of resinous material.
 12. A method in accordance with claim 4 inwhich the energy applied through direct-heat isolating films ofpolyester resinous material for heating the contiguous portions of thefirst and second films of resinous material along their interface isheat, the heat being applied to the outermost expendable film ofresinous material on both sides of the first and second films ofresinous material.
 13. A method in accordance with claim 4 in which theenergy applied through the direct-heat isolating films of polyesterresinous material on both sides of the first and second films ofresinous material for heating the contiguous portions of the first andsecond films of resinous material along their interface is ultrasonicenergy.